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Biomedical subjects

F E Harrell

Publications and source records attributed to F E Harrell.

At least 109 records · Page 6Linked to original sources
PubMed1984

Prognostic indicators from radionuclide angiography in medically treated patients with coronary artery disease.

The purpose of this investigation was to determine which variables obtained when performing radionuclide angiography predict subsequent survival or total events (cardiovascular death or nonfatal myocardial infarction) in stable patients with symptomatic coronary artery disease (CAD). Univariable and multivariable analyses of 6 variables, including ejection fraction (EF) at rest and exercise, change in EF with exercise, development of ischemic chest pain or electrocardiographic changes, left ventricular (LV) wall motion abnormalities and exercise time were examined in 386 patients followed up to 4.5 years. Univariate analyses revealed that the exercise EF was the variable most closely associated with future events (p less than 0.01), followed by EF at rest, wall motion abnormalities and exercise time. Multivariable analyses revealed that once the exercise EF was known, no other radionuclide variables contributed independent information about the likelihood of future events. Multivariable analyses also revealed that the exercise EF describes much of the prognostic information of coronary anatomy. Our findings suggest that the radionuclide angiogram is useful in predicting future events in patients with stable CAD, although examination in conjunction with other clinical descriptors will be necessary to further quantify this contribution.

Cardiac Output↗
PubMed1984

Factors affecting sensitivity and specificity of exercise electrocardiography. Multivariable analysis.

Unlike the predictive value of a diagnostic test, which depends on the prevalence of disease in the population tested, its sensitivity and specificity have been assumed to be constants. This assumption was examined in patients who had both exercise electrocardiography and cardiac catheterization. The effects on sensitivity of factors from clinical history, catheterization, and exercise performance were defined by multivariable logistic regression analysis in 1,401 patients with coronary disease; effects on specificity were defined by a similar analysis in 868 patients without coronary disease. Five factors had significant, independent effects on exercise electrocardiographic sensitivity: maximal exercise heart rate, number of diseased coronary arteries, type of angina, and the patient's age and sex. Only maximal exercise heart rate had a significant, independent effect on exercise electrocardiographic specificity. Thus, the sensitivity and specificity of exercise electrocardiography vary with clinical history, extent of disease, and treadmill performance; the sensitivity and specificity of other diagnostic tests may also vary.

Adult↗
PubMed1984

The effect of crossovers on estimates of survival in medically treated patients with coronary artery disease.

Among 1661 consecutive patients with significant coronary artery disease treated medically at the Duke University Medical Center, 239 have undergone aortocoronary bypass surgery after at least 6 months of medical management. The purpose of this investigation was twofold: (1) to identify the distinguishing characteristics of these treatment crossovers; and (2) to illustrate a method of estimating the effect that withdrawing the crossovers from the analysis would have on the survival of the medically managed patients. Of 81 baseline characteristics compared, 25 were significantly (p less than 0.05) different between crossovers and noncrossovers. These included five characteristics that had previously been determined to be independent predictors favoring improved survival in medically treated coronary artery disease. A Cox regression analysis identified six variables independently associated with the time until crossover surgery. Crossover patients were younger and had superior ventricular function. A hazard score, which summarized in a single variable the overall risk of mortality, was developed from the prognostic baseline characteristics. Crossover patients had significantly (p = 0.003) lower hazard scores and hence would have been expected to have a superior survival compared with noncrossover patients. In our series, survival in the medically treated patients would likely have been higher had the crossovers remained in the medical group.

Coronary Artery Bypass↗
PubMed1984

Ventricular fibrillation following canine coronary artery reperfusion: different outcomes with pentobarbital and alpha-chloralose.

We compared the incidence of ventricular fibrillation after release of a 20 min-proximal left anterior descending coronary artery ligation in dogs anesthetized with either pentobarbital (N = 26) or morphine sulfate plus alpha-chloralose (N = 26). Results were analyzed using the logistic risk regression model. In each group, outcome correlated with the amount of myocardium perfused by the ligated vessel (myocardium "at risk") as measured by postmortem coronary injection of monastral dyes. At any given myocardium at risk, animals anesthetized with alpha-chloralose were less likely to fibrillate after release than those anesthetized with pentobarbital (p less than 0.01). This difference in outcome can be described by the myocardium at risk at which half the animals are expected to fibrillate (MAR50). MAR50 was 20.9 g for the pentobarbital group and 30.7 g for the alpha-chloralose group. Myocardium at risk should be taken into account in intervention studies using this coronary reperfusion arrhythmia model. We chose the logistic risk regression model to correct for this variable because it allowed a good fit of the data and offered a concise standard format for expressing the results. Outcome in reperfusion studies may be influenced by the choice of anesthetic agent.

Anesthesia↗
PubMed1984

Clinical characteristics and long-term survival of patients with variant angina.

We studied 109 consecutive patients with variant angina who underwent cardiac catheterization over an 11 year period. All patients were followed for at least 6 months or until death, and 46 patients (22 treated medically and 24 treated surgically) were followed for 5 years or more. Of the 62 patients initially treated medically, 14 had nonfatal myocardial infarctions (12 within 1 month of catheterization) and 12 died (six within 6 months). Survival probabilities at 1, 3, and 5 years were 0.88, 0.84, and 0.77, respectively. Of the 48 surgically treated patients (including four patients initially treated medically and one initially treated with coronary angioplasty), four had nonfatal infarctions (three in the perioperative period) and three died (all in the perioperative period). The survival probability in these patients at 1 year was 0.94 and remained unchanged at 3 and 5 years. Only one nonfatal infarction and no deaths have occurred in the group of surgically treated patients subsequent to hospital discharge. Three additional patients were treated with coronary angioplasty. The single most important prognostic factor in medically treated patients was the presence or absence of fixed obstructive coronary artery disease. Infarction-free survival probabilities at 1 and 3 years in the 23 patients without significant coronary artery disease were 1.0 and 0.89, compared with 0.51 and 0.46 in the 39 patients with significant coronary disease. Analysis by the Cox model showed that variant angina patients had a higher probability of death and nonfatal infarction than did those with nonvariant angina coronary disease if other important prognostic variables were held constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris, Variant↗
PubMed1983

An improving prognosis over time in medically treated patients with coronary artery disease.

The national mortality rate from coronary heart disease has decreased during the past decade, for reasons that are not yet clear. The mortality rate and the total number of cardiovascular events both decreased during the last 10 years in 1,911 medically treated patients with significant coronary artery disease. This decrease cannot be explained by less sick patients being referred for evaluation. This study suggests that at least part of the decrease in coronary heart disease mortality observed nationally is occurring in patients with established coronary disease.

Coronary Disease↗
PubMed1983

Natural history of patients with single-vessel disease suitable for percutaneous transluminal coronary angioplasty.

To permit comparison of percutaneous transluminal coronary angioplasty (PTCA) with conventional therapy, the clinical outcome was established in patients who would have been suitable candidates for PTCA but who presented before the technique was available. Coronary angiograms were reviewed of patients who met the following criteria: single-vessel disease with proximal subtotal coronary stenosis, chest pain of at least class II, and cardiac catheterization before 1981. Angiograms were evaluated according to established criteria for PTCA by an experienced angiographer. One hundred ten patients (2.1% of the patient population) were judged suitable for PTCA. Clinical and catheterization findings closely resembled those of patients in the national PTCA registry. Five years after catheterization, 97% of PTCA candidates treated medically were alive and 85% had not had myocardial infarction. Forty-six patients had coronary artery bypass surgery within 6 months of catheterization and 10 other patients had subsequent surgery. Five years after surgery, 91% were alive and 87% had not had myocardial infarction. At 6 months of follow-up, 78% of all patients had improved at least 1 functional class, and 86% of all patients working before catheterization were still employed. Functional capacity was well maintained during long-term follow-up (median 6.5 years, range 1.4 to 12.2). These data indicate that PTCA candidates have an excellent prognosis for survival, a low risk of infarction, and well-maintained functional capacity when revascularization is reserved for those with inadequate control of symptoms by medical therapy.

Angioplasty, Balloon↗
PubMed1983

Estimating the likelihood of significant coronary artery disease.

Among 23 clinical characteristics examined in 3,627 consecutive, symptomatic patients referred for cardiac catheterization between 1969 and 1979, nine were found to be important for estimating the likelihood a patient had significant coronary artery disease. A model using these characteristics accurately estimated the likelihood of disease when applied prospectively to 1,811 patients referred since 1979 and when used to estimate the prevalence of disease in subgroups reported in the literature. Since accurate estimates of the likelihood of significant disease that are based on clinical characteristics are reproducible, they should be used in interpreting the results of additional noninvasive tests and in quantitating the added diagnostic value.

Adult↗
PubMed1983

Prognostic value of ventricular arrhythmias associated with treadmill exercise testing in patients studied with cardiac catheterization for suspected ischemic heart disease.

The prognostic information provided by ventricular arrhythmias associated with treadmill exercise testing was evaluated in 1,293 consecutive nonsurgically treated patients undergoing an exercise test within 6 weeks of cardiac catheterization. The 236 patients with simple ventricular arrhythmias (at least one premature ventricular complex, but without paired complexes or ventricular tachycardia) had a higher prevalence of significant coronary artery disease (57 versus 44%), three vessel disease (31 versus 17%) and abnormal left ventricular function (43 versus 24%) than did patients without ventricular arrhythmias. Patients with paired complexes or ventricular tachycardia had an even higher prevalence of significant coronary artery disease (75%), three vessel disease (39%) and abnormal left ventricular function (54%). In the 620 patients with significant coronary artery disease, patients with paired complexes or ventricular tachycardia had a lower 3 year survival rate (75%) than did patients with simple ventricular arrhythmias (83%) and patients with no ventricular arrhythmias (90%). Ventricular arrhythmias were found to add independent prognostic information to the noninvasive evaluation, including history, physical examination, chest roentgenogram, electrocardiogram and other exercise test variables (p = 0.03). Ventricular arrhythmias made no independent contribution once the cardiac catheterization data were known. In patients without significant coronary artery disease, no relation between ventricular arrhythmias and survival was found.

Arrhythmias, Cardiac↗
PubMed1983

Outcome in one-vessel coronary artery disease.

We analyzed the clinical outcomes in 688 patients with isolated stenosis of one major coronary artery. The survival rate among patients with disease of the right coronary artery (RCA) was higher than that among patients with left anterior descending (LAD) or left circumflex coronary artery (LCA) disease. The survival rate among patients in all three anatomic subgroups exceeded 90% at 5 years. The presence of a lesion proximal to the first septal perforator of the LAD was associated with decreased survival compared with the presence of a more distal lesion. For the entire group of one-vessel disease patients, total ischemic events (death and nonfatal infarction) occurred at similar rates regardless of the anatomic location of the lesion. Left ventricular ejection fraction was the baseline descriptor most strongly associated with survival, and the characteristics of the angina had the strongest relationship with nonfatal myocardial infarction. No differences in survival or total cardiac event rates were found with surgical or nonsurgical therapy. The relief of angina was superior with surgical therapy, although the majority of nonsurgically treated patients had significant relief of angina. The survival rate of patients with one-vessel coronary disease is excellent, and the risk of nonfatal infarction is low. Clinical strategies for the care of these patients must consider the long-term clinical course of one-vessel coronary disease.

Angina Pectoris↗
PubMed1983

The use of radionuclide angiography in the diagnosis of coronary artery disease--a logistic regression analysis.

We applied logistic regression analysis to a group of 736 patients with chest pain to determine which radionuclide angiographic (RNA) parameters were most useful in the diagnosis of significant coronary artery disease. The most useful parameters were exercise ejection fraction, exercise heart rate, "ischemia score," and the presence of a regional wall motion abnormality at exercise. Ten clinical variables were used in one logistic regression model to estimate each patient's pretest probability of disease. A second logistic regression model considered these clinical variables and the four important RNA parameters to estimate each patient's posttest probability. These models were applied prospectively to a group of 76 patients with chest pain who did not have a high pretest probability of disease. Twenty-four patients (32%) could be diagnosed with 90% probability; 32 patients (42%) could be diagnosed with 85% probability. RNA testing is therefore helpful in the noninvasive diagnosis of coronary artery disease. However, a majority of patients who do have a low or intermediate pretest probability of disease will require additional testing for a definitive diagnosis.

Cardiac Catheterization↗
PubMed1983

The prognosis for patients with new-onset angina who have undergone cardiac catheterization.

We investigated the prognostic significance of new-onset angina in patients in whom coronary anatomic characteristics were known. New onset angina was defined as angina of less than 3 months duration. Consecutive patients (n = 1727) with significant coronary artery disease (diagnosed at cardiac catheterization) and who had not had a prior myocardial infarction or congestive heart failure were studied. In patients with new-onset angina (n = 329) there was a higher incidence of single-vessel disease (43% vs 27%) and a lower incidence of triple-vessel (23% vs 35%) and left main artery (5% vs 10%) disease compared with patients with chronic angina (n = 1398). Patients were classified by the presence or absence of preinfarction angina (severe and prolonged angina at rest requiring hospitalization to rule out myocardial infarction). In patients treated without surgery and who did not have preinfarction angina, survival at 1 year was 97% for patients with new-onset angina and 98% for those with chronic angina (p = .27). Among patients not treated surgically who did not have preinfarction angina, at 1 year 16% with new-onset angina and 7% with chronic angina had suffered a cardiac event (nonfatal myocardial infarction or death, p = .006). In patients treated surgically who did not have preinfarction angina, survival at 1 year was 96% both for those with new-onset angina and those with chronic angina (p = .99). The risk of an event in patients treated surgically at 1 year was not statistically different in patients with new-onset angina and those with chronic angina (12% vs 11%, p = .27). Survival and event-free rates were lower in patients with preinfarction angina than in patients who did not have it.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1983

A comparison of test statistics for assessing the effects of concomitant variables in survival analysis.

In data analysis involving the proportional-hazards regression model due to Cox (1972, Journal of the Royal Statistical Society, Series B 34, 187-220), the test criteria commonly used for assessing the partial contribution to survival of subsets of concomitant variables are the classical likelihood ratio (LR) and Wald statistics. This paper presents an investigation of three other test criteria with potentially major computational advantages over the classical tests, especially for stepwise variable selection in moderate to large data sets. The alternative criteria considered are Rao's efficient score statistic and two other score statistics. Under the Cox model, the performance of these tests is examined empirically and compared with the performance of the LR and Wald statistics. Rao's test performs comparably to the LR test in all the cases considered. The performance of the other criteria is competitive in many cases. The use of these statistics is illustrated in a study of coronary artery disease.

Analysis of Variance↗
PubMed1983

'Reactive gliosis' in the medulla oblongata of victims of the sudden infant death syndrome.

A current hypothesis that the sudden infant death syndrome (SIDS) is a sleep apnea syndrome precipitated by defective control of involuntary respiration prompted the present study in which "reactive gliosis" in sections of the medulla oblongata of 45 SIDS victims was quantitated and compared with that in 20 control infants. Six anatomic regions were studied; five are related and one is unrelated to neural control of involuntary respiration. Increased numbers of "reactive" astrocytes were found in the SIDS group when the counts for all regions were combined (P = .04). Counts were also significantly higher in the SIDS victims for each of three regions alone: (1) the hilum of the inferior olivary nucleus (P = .01); (2) a lateral region (P = .02); and (3) the nucleus of the tractus solitarius (P = .03). The region with the greatest statistical difference, the inferior olivary hilum, has no recognized role in the control of involuntary respiration. There were no consistent associations between reactive astrocyte counts and specific clinical, socioeconomic, and pathologic variables. Characterization of the SIDS group whose counts exceeded that of the highest control infant also did not uncover distinguishing features. This study reinforces previous observations that, at least statistically, an abnormality of the brainstem occurs in a group of SIDS victims in contrast to a group of control infants, but also discloses considerable overlap in the numbers of such cells between these two groups.

Astrocytes↗
PubMed1982

Evaluating the yield of medical tests.

A method is presented for evaluating the amount of information a medical test provides about individual patients. Emphasis is placed on the role of a test in the evaluation of patients with a chronic disease. In this context, the yield of a test is best interpreted by analyzing the prognostic information it furnishes. Information from the history, physical examination, and routine procedures should be used in assessing the yield of a new test. As an example, the method is applied to the use of the treadmill exercise test in evaluating the prognosis of patients with suspected coronary artery disease. The treadmill test is shown to provide surprisingly little prognostic information beyond that obtained from basic clinical measurements.

Catheterization↗
PubMed1982

A QRS scoring system for assessing left ventricular function after myocardial infarction.

A QRS scoring system for estimating the size of a myocardial infarct was evaluated in 55 patients who did not have left ventricular hypertrophy or conduction abnormalities. Serial 12-lead surface electrocardiograms were scored according to a 29-point system based on the duration of Q and R waves and on the ratios of R-to-Q amplitude and R-to-S amplitude. The scores were proportional to the severity of wall-motion abnormalities, which was determined by radionuclide blood-pool scanning and which correlated inversely with the radionuclide-determined left ventricular ejection fraction (LVEF). A score less than 3 was 93 per cent sensitive and 88 per cent specific for both severe regional dyssynergy and major depression of the global LVEF. The following equation was used to estimate the LVEF from the QRS score: LVEF (%) = 60 - (3 x QRS score). After acute myocardial infarction, an electrocardiogram can provide important indirect quantitative information about left ventricular function.

Electrocardiography↗
PubMed1982

Prognostic implications of ventricular arrhythmias during 24 hour ambulatory monitoring in patients undergoing cardiac catheterization for coronary artery disease.

The prognostic importance of ventricular arrhythmias detected during 24 hour ambulatory monitoring was evaluated in 395 patients with and 260 patients without significant coronary artery disease. Ventricular arrhythmias were found to be strongly related to abnormal left ventricular function. A modification of the Lown grading system (ventricular arrhythmia score) was the most useful scheme for classifying ventricular arrhythmias according to prognostic importance. When only noninvasive characteristics were considered, the score contributed independent prognostic information, and the complexity of ventricular arrhythmias as measured by this score was inversely related to survival. However, when invasive measurements were included, the ventricular arrhythmia score did not contribute independent prognostic information. Furthermore, ejection fraction was more useful than the ventricular arrhythmia score in identifying patients at high risk of sudden death.

Adrenergic beta-Antagonists↗